The subaërial deposits now accumulating in the arid portion of the United States may be divided into four classes: 1, Eolian Sands; 2, Talus Slopes; 3, Alluvial Cones; and 4, Calcareous Clays to which no specific name has been applied, but which, for reasons stated below, will be called “adobe” in this paper.

When the new railway from Nottingham to Market Harborough was made, several instructive sections in the Upper and Middle Lias series were opened out between the latter place and Tilton. Most of these are now covered up and grass-grown, but one of the best is still partially laid bare in the deep cutting at Tilton Station. This Tilton section has become one of considerable interest to the geologists of the Midland district, from the complete and characteristic exposure which it gives of the Marlstone Rock of Leicestershire in its fully developed and unweathered form, and also on account of the rich fauna which that rock, and in particular its top or ‘Transition Bed,’ has here yielded.

The convergence of opinion is now so strong that the climate of Siberia in the Mammoth age was sufficiently temperate to enable trees to grow where only the bare tundra is at present found (if it does not necessitate our extending the forest zone at least as far north as the Liachof Islands), that it becomes at once interesting and important to consider under what conditions such a result would be forthcoming.

The commonly-received theory that most coal-seams represent vegetable matter that has grown and has been entombed on the spot has never been received by all geologists with quite that measure of satisfaction that has been accorded to other theories of the same general nature. It has been felt again and again that the explanation referred to might be true enough for certain cases; but that in others it failed to account satisfactorily for all the phenomena. It involved too many complications—too nice an adjustment of the rate of growth of the vegetation to the rate of subsidence and of sedimentation—too much straining of the theory in question generally—to be accepted unhesitatingly by those accustomed to judge of such facts for themselves. That certain beds of coal have been formed by the growth of vegetation on the spot no reasonable person can doubt: the only question is whether that is true of every coal-seam.

More than one kind of rock, as we learn from Dr. H. Hicks and other writers, occurs in the conglomerate which forms a well-marked base to the Cambrian system at St. Davids. Sometimes the pebbles are mainly vein quartz, sometimes felstone predominates, but occasionally, as in the neighbourhood of Nun's Chapel Bay, quartzites (using the term rather generally) are not uncommon. At one place, not far from a quartz-felsite dyke, these are rather large, occasionally about a foot in diameter. From this locality, while spending a few days at St. Davids in 1882, I brought away specimens of three of the most marked varieties of quartzite, of which I had slices prepared, thinking that as examples of rocks which were probably far from modern at the beginning of the Cambrian age, their structures might be instructive.

The Archæan question in this country may be said to be about twelve years old. Rocks older than the Cambrian had indeed been recognized by Murchison and Sedgwick, and brief notices of Pre-Cambrian masses at St. Davids had been published by Salter, Harkness, and Hicks; but the Archæan campaign was formally opened by Dr. Hicks in a paper read before the Geological Society in November, 1876. The attack upon the old views was followed up by Prof. Bonney, the Rev. Edwin Hill, Prof. Hughes, and myself, and, more recently, by Prof. Lapworth and Prof. Blake. The defence has been conducted by Dr. A. Geikie. The controversy has been animated, and not without sensational incidents. Great diversity of opinion has existed even amongst the assailants, and many important divisions of the inquiry must be still regarded as unsettled.

Having occasion in a work now in the press to refer to certain fossil Reptiles and Amphibians of which the commonly accepted nomenclature requires revision, I think it advisable to make the necessary amendments in a Journal specially devoted to Geology and Palæontology. I also take the opportunity of giving two new scientific names to Reptiles from the Wealden.